CCD-world: Reset gate threshold shift

[GregJ888 at aol.com]

The following was posted to CCD-world:

ESD is surprisingly misunderstood.  Many of the continuity monitors work by 
placing a constant current source on the operator and will peak at or above 
18v DC.  To check -- measure from the sense portion of the wrist strap to 
ground with a volt meter (or unground the wrist strap but leave the monitor 
grounded).  Also check the operator when strapped, some units don't alarm 
until above 12v.  Shunt the strap to ground with a variable resister.  Find 
the set point where the alarm sounds and measure with you volt meter.  

Some other things we've found (measurements below are dV/dT field 
measurements):

1) "ESD dissipative" freeze spray is capable of generating a 2000v field when 
sprayed-- as are will most spray cleaners.  Tribo-charging of the liquid 
moving though the nylon spray tube.  I keep ALL sprays away from static 
sensitive devices.

2) Charge/Cap= Vconstant right?  If the Charge is on the human body, then by 
lifting 1 foot (Cap/2), V about doubles.

3) Silk tie, 2000v.  Boss's ESD smock has to be zipped all the way up.

4) Charge separation, i.e. getting out of a chair-- 1000v easy, 2000v if 
humidity is low.  So stand up , then take the wrist strap off.  

5) A broken hand held ionizer will put out +100v.  

FYI- I have a business relationship with Novx so be advised.  Their monitors 
are use in the disk drive industry with a 5v ESD limit settable to 1v.  Sorry 
about the plug, further info- <A HREF="http://www.novxcorp.com/">Novx</A>   
Check out the 53XX, that's what's on my bench when a cryostat is open.

Greg Jones

In a message dated 4/24/00 1:25:26 PM Pacific Daylight Time, 
roger at ctios1.ctio.noao.edu writes:

<< 
 What could have happened?  Static discharge is rarely a problem in our
 very humid environment.  Nonetheless, the CCD has always been handled
 on properly grounded antistatic mats (bench and floor) while using a
 wrist strap with a continuity alarm.  Remember too that I obtained
 normal images with normal voltages immediately prior to taking the CCD
 to Cerro Tololo and it was kept under vacuum and cold the whoel time
 until it ceased to operate.
  >>
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